Apparatus for rolling seamless tubes

ABSTRACT

A process for rolling seamless tubes and apparatus for performing the process is disclosed. The process is an improvement over the known process in which a tube is rolled on a mandrel which is restrained at its head end, and after the rolled tube is discharged the mandrel is moved laterally to a cooling position and a second mandrel used for a subsequent rolling operation, the two mandrels alternating between a cooling position and an operating position. The improvement comprises using a single mandrel and cooling this whilst it remains on the rolling axis. The mandrel never leaves the rolling axis, being moved backwards and forwards along this during rolling and cooling stages of the process. The apparatus includes tubular tanks between adjacent roll stands of the rolling mill through which the rolled tube and mandrel pass and in which the cooling is effected by a flow of coolant therethrough.

iJiiited States Patent i191 Calmes 1 Nov. 25, 1975 [5 1 APPARATUS FOR ROLLING SEAMLESS 3,782,160 H1974 Kheifets et al 72/201 TQQES 3,805,568 4/1974 Properzi [75] Inventor: Jean Paul Calmes, Lausanne, Switzerland [73] Assignee: Innocenti Santeustacchio S.p.A., Brescia, Italy [22] Filed: Nov. 12,, 1974 [21] Appl. No.: 523,178

Related U.S. Application Data [62] Division of Ser. No. 435,046, Jan. 21, 1974,

abandoned.

[30] Foreign Application Priority Data Jan. 23, 1973 ltaly 19496/73 [52] U.S. Cl. 72/201 [51] Int. Cl. B21B 45/02 [58] Field of Search 72/4l45, 96,

[56] References Cited UNITED STATES PATENTS 1,931,912 10/1933 Whitzel 72/201 2,245,656 6/1941 Engelbaugh et al. 72/97 3,392,565 7/1968 Rodder 72/201 3,394,568 7/1968 Calmes 72/41 3,577,754 5/1971 Calmes 72/45 Primary Examiner-C. W, Lanham Assistant Examiner-E, M. Combs Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A process for rolling seamless tubes and apparatus for performing the process is disclosed. The process is an improvement over the known process in which a tube is rolled on a mandrel which is restrained at its head end, and after the rolled tube is discharged the mandrel is moved laterally to a cooling position and a second mandrel used for a subsequent rolling operation, the two mandrels alternating between a cooling position and an operating position. The improvement comprises using a single mandrel and cooling this whilst it remains on the rolling axis. The mandrel never leaves the rolling axis, being moved backwards and forwards along this during rolling and cooling stages of the process. The apparatus includes tubular tanks between adjacent roll stands of the rolling mill through which the rolled tube and mandrel pass and in which the cooling is effected by a flow of coolant therethrough.

4 Claims, 4 Drawing Figures US Patent Nov. 25, 1975 Sheet1of2 3,921,430

US. Patent Nov. 25, 1975 Sheet20f2 3,921,430

w h m m APPARATUS FoR ROLLING sEAMLEss TUBES This is a division of application Ser. No. 435,046. filed Jan. 21, l974. now abandoned.

BACKGROUND OF THE INVENTION The present invention relatesto a process for rolling seamless tubesyof the type in which an inget or bloom to be formed into a tube is passed. through a train of rolls on a mandrel which is restrained at its upstream end, following which the mandrel is cooled before being re-used.

This invention also relates to apparatus for carrying the processinto effect, comprisinga train of rolls and an arrangement, upstream of the train of rolls, for controlling the movement of mandrel inserted in a hollow ingot or bloom to be rolled.

In known processes of. this type a hollow ingot or bloom is arranged on a support in front of a multiplestand rolling mill and a mandrel is inserted through the full length of the ingot which is then introduced between the rolls. In thisarrangement the head of the mandrel is carried on an initially fixed restraining crosspiece, and with the introduction of the bloom between the first pair of rolls', the controlled forward movement of the restraining crosspiece is commenced. The controlled movement is effected in one known apparatus by removing at a controlled rate by a constant discharge pump the oil contained in hydraulic cylinders to the actuating members of which the crosspiece is attached. In this way the speed of advance of the mandrel is controlled to an acceptable value, which depends on the admissable degree of heating for the surface of the mandrel.

The mandrel of known types of such apparatus is lubricated duringrolling by injection of a lubricant between the inner surface ofthe bloom and the outer surface of the mandrel through a conduit inside the mandrel itself; there is also a conduit within the mandrel through which a continuous flow of cold water under pressure is maintained during rolling for cooling purposes (see for example French Pat. No. 1458432). After rolling the tube and extraction of the mandrel. the latter, fixed to a longitudinal transport device is drawn out of the rolling mill to be returned to the starting position to commence another cycle. In order completely to cool the mandrel, it is thrust laterally of the rolling axis to an.outer cooling position beneath spray jets, whilst a second mandrel which was in the cooling position under the jets during the working cycle of the.

firstmentioned mandrel. is automatically moved to the starting position as a result of displacement of the first mentioned mandrel to the cooling position.

Such processes in which two mandrels are used alternately provides a fairlysatisfactory hourly working rate. but this process does have certain disadvantages:

the time taken for inserting. extracting, return and lateral movement of the mandrel, represents a loss of productive time so that actual rollingoccupies less than 50% the productive duration of the total cycle: i v j therolling mill requires a costly installation for longitudinal and transverse transport of the mandrels:

when it becomes necessary to change mandrels the fact that they are fixed to the device for moving the mandrels, entails extra loss of time and further lowers the production rate? OBJECT AND SUMMARY OF THE INVENTION The object of the present invention is to reduce substantially the disadvantages of known processes mentioned above by providing a rolling process of rational,-

conception and noteworthy efficiency.

According to one aspect of the present invention there is provided a process for rolling seamless tubes. comprising a rolling stage in which the ingot or bloom to be rolled into a tube is passed through a roll train on a mandrel restrained at its head end by a restraining device. and a cooling stage, characterised in that after dis-.

charge of the-rolled tube. the mandrel is moved longitudinally and maintained on the rolling axis whilst being cooled and is then moved longitudinally along said rolling axis into position for the commencement of a subsequent operative cycle.

According to another aspect of the present invention apparatus for carrying out the process defined above comprises a roll train and a restraining device upstream of the roll train operable to restrain and to move in a controlled manner the mandrel. when attached thereto. characterised in that it includes tubular tanks located on the rolling axis between adjacent stands of the roll train and connected to conduits for admission and discharge of a coolant liquid. there being provided valves to control the admission of coolant liquid into the tubular tanks during the cooling stage of the process and to effect discharge ofthe coolant liquid from the tanks immediately before the rolling stage of the process.

The advantages obtained with embodiments of this invention include a considerable reduction A in time wasted in cooling the mandrel. since this is largely effected whilst the mandrel is moved upstream-of the rolls on the rolling axis to be re-used in the next rolling operation. and a simplification of the apparatus since lateral transport devices for the mandrels are no longer required.

Various other features and advantages of the invention will become more apparent during the course of the following particular description in which reference is made to the accompanying drawings, which is provided purely by way of non-restrictive example.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic longitudinal section of a rolling mill equipped to carry out the process of thisinvention;

FIG. 2 is an axial section on an enlarged scale illustrating a detail of the embodiment of FIG. 1;

FIGS. Sand 4 are cross sections taken on the line III- III of FIG. 1, illustrating the apparatus during and after the passage of an ingot.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 3, the rolling'mill A which is of continuous type having a plurality of roll stands. The embodiment illustrated in FIG. 1 is a five-stand rolling mill each stand of which comprises a pair of rolls a. For the sake of simplicity in FIG. 1 the rolls a have been shown all with parallel axes. but in practice the axes of the rolls of the second and fourth stand would be perpendicular to the axes of the rolls of the other stands.

At the commencement of a cycle of operation. when the bloom l is in position on the rolling axis of the mill A. a hollow mandrel 2is inserted at high speed ino the bloom from the downstream end thereof. being moved in the direction opposite the direction of rolling by means of high-speed movement cylinders 4 which are located at the input end of the rolling mill A and which are movable into and out of an engagement position by means of respective hydraulic cylinders 4a. Immediately afterwards. the head 3 ofthe mandrel is automatically coupled to a restraining crosspiece 5 and at the same time (and also automatically) couplings are made to cooling water conduits 6 which extend through the mandrel 2, for cooling the inside thereof. and to lubricant conduits 7, which have outlets on the outer face of the mandrel 2 for lubricating the inner face of the bloom l..The system for cooling the inside of the mandrel 2 and for lubricating the-internal surface of the bloom l is known in itself and may for example be the same as-thatshown in French Pat. No. l.458.432.

Movement of the crosspiece 5 during rolling is controlled by hydraulic cylinders 9 which are themselves controlled to move at constant speed by means of a constant-discharge pump (not shown). The crosspiece 5 is-thus movable during a rolling operation to the position shown in broken outline in FIG. 1. On the rolling axis and between one pair of rolls and the next. there are provided tubular tanks 12 through which the tube 1 being rolled and the mandrel 2 can pass-during the rolling operation;

The underside of each tubular tank 12 has a dis charge opening 13 and the upper part of each tank has an aperture 13a (FIG. 2). Also. for each tank 12, there is provided a vertically movable saddle support 11 which can be moved between a raised position in "which it is inserted into the discharge opening 13, so as to close it, and a lowered position in which the opening 13 is unobstructed. In the raised position each support 11 projects a certain distance into the respective tubular tank 12. Each saddle support 11 has a surrounding collar lla engageable with a cooperating annular abutment 13b, provided around the opening 13, when the support 11 is raised. The supports 11 serve. in the raised position, for supporting the mandrel 2 after a rolling operation. and are raised and lowered by means of respective hydraulic cylinders 11b (FIG. I).

The tubular tanks 12 also have conduits 14 communicating with the underside thereof. through which cooling water can be introduced into and withdrawn from the tanks. Each conduit 14 has a three-way valve 14a by means of which the conduit 14 can be connected to a main supply conduit 14b or with a discharge conduit 140 depending on the position of the valve 14a.

Downstream of the rolling mill A there are placed two further tubular tanks 1211 which are the same as tanks 12; these are also supplied with cold water by conduits 14 from the main supply conduit 14b, and n have movable supports 11 (FIG. 1). The continuous arrows B (FIG. 2) indicate the flow of water when the valves 140 are moved to a position allowing admission of water to the tanks 12. 12a. whilst the dashed arrows C indicate the outgoing flow when the valves [40 are moved to the discharge position.

Between the tubular tanks 12a located downstream of the rolling mill A there is provided a rotary movement device 8, comprising a pair of inclined rolls operative to move the mandrel 2 longitudinally and at the same time to cause it to rotate around its longitudinal axis.

Downstream of the tubular tanks 12a there is a calibrator-extractor rolling mill 10 of known type.

The manner of operation of the abovementioned apparatus is as follows:

Internal cooling ofthe mandrel 2 takes place by passing cooling water into a tube 2a arranged coaxially within the mandrel 2 in the direction of the arrow D of FIG. 2. The tube 2a is shorter than the mandrel 2 and open ended whereas the mandrel 2 is closed at the end so that the water flow returns in the direction of the arrow E in the space between that tube 2:: and the inner surface of the mandrel 2. This arrangement is shown in French Pat. No. 1,458,432. External cooling of the mandrel 2 is effected in the tubular tanks 12 and 12a. Only one mandrel 2 is required for the apparatus. in contradistinction with previously known apparatus in which two mandrels were required. The mandrel is inserted. at the start of the rolling cycle. into the bloom l, by moving it upstream on the rolling axis until the head 3 engages the crosspiece 5. to which it couples up automatically (the movement of the mandrel upstream of the rolling mill is effected by high-speed displacement rollers 4). After this the rolling can be started by insertion of the bloom 1 (together with the mandrel 2) into the rolling mill A. movement being effected by the crosspiece 5.

A few seconds before the front end of the bloom l enters between the rolls of the roll stands the supports 11 are successively and automatically lowered thus opening the discharge orifices 13, whilst the conduits 14 are connected to the discharge conduits by turning the valves 14a to the appropriate position as described above.

When the supports 11 are lowered the openings 13 are unobstructed; the water thus drains from the tubular tanks 12 and 12a and is not replenished since the conduits 14 are also connected to the discharge conduits 14c. Rolling of the tube then takes place regularly with the passage of the tube 1 and mandrel 2 through the tanks 12 and 12a. Immediately after the rolled tube 1 has been discharged from the roll stands. the mobile supports 11 are progressively raised so that they close the openings 13 and at the same time support the mandrel 2 which extends between the main rolls but does not touch them. Simultaneously. the cooling water admission conduits 14 are opened in turn by rotation of the volves 14a to the appropriate position. Thus transi-' tion is made from the arrangement shown in FIG. 3 which shows the supports 11 in the lowered position, the tubular tanks 12 empty and the mandrel 2 and tube 1 passing therethrough, to the position shown in FIG. 4 in which the supports 11 are raised until the collar 11a encounters the annular abutment 13b so as to support the mandrel 2 after the rolled tube 1 has been drawn therefrom by the action of the roll train A, and the tubular tanks 12 are refilled with cooling water flowing continuously from the conduits 14 into the tanks 12 and overflowing from the tops of the tanks 12 through the apertures 13a. The tube 1 is removed from the rolling mill A by the calibrator-extractor rolling mill 10.

After the rolled tube 1 has been discharged the mandrel 2 is uncoupled from the crosspiece 5 and thus also from the cooling water conduits 6 and the lubricant conduits 7. Whilst the cross piece 5 is quickly returned to its initial position by means of the hydraulic cylinders 9, the mandrel 2 is moved axially first forwards. that is in the same direction as it travels during rolling. and then backwards by means of the movement device 8 which, as mentioned above, causes the mandrel both to move axially and to rotate around its axis. With these movements the mandrel 2 is effectively cooled over its external surface in the tubular tanks 12 and 12a which. in this stage of the process, as stated, are full of running water.

The movement device 8 operates to drive the mandrel in the reverse direction of movement through the next bloom to be rolled which has been placed in position before the head 3 of the mandrel 2 passes out of the roll train A in its reverse movementv The head 3 of the mandrel is thus re-engaged with the crosspiece 5 ready for the commencement of the next rolling operation.

The mandrel 2 is thus re-utilized for each rolling operation; it is maintained constantly on the rolling axis of the rolling mill, and inserted from downstream to upstream in each bloom l to be subjected subsequently to rolling.

As the mandrel 2 returns to the initial position, the supports 11 will be lowered automatically after the mandrel has passed, so as to open the discharges 13; the conduits 14 are at the same time placed in communication with the discharge conduit. The tanks 12 and 12a will thus empty so to be ready to receive the mandrel 2 and the tube 1 in the subsequent rolling operation.

It will be appreciated that the process according to this invention makes possible the continuous use of a single mandrel 2, permitting it to be cooled upon the actual rolling axis of the rolling mill. Cooling takes place continuously from the moment the rolled tube is discharged almost until the mandrel itself is reconnected to the crosspiece 5.

To replace a worn or damaged manrel it may be withdrawn from the diischarge end of the mill A in a similar manner to that of a rolled tube, or alternatively may be removed from the entry end of the mill A so that it can be replaced by a new mandrel.

The fact that the mandrel 2 after cooling is projected by the movement device 8 towards the starting position, without the need for previous attachment of the mandrel to the crosspiece 5 makes it possible to increase the separation between adjacent roll stands of the roll train A, with respect to known systems, thus allowing larger dimensions of the mechanical members of the stands themselves.

The invention thus conceived is capable of numerous variations and modifications all entering into the scope of this invention. For example, in place of a single helical movement device 8, two or more such devices may be used.

LII

Similarly, the helical movement device 8 may be constituted by any means suitable for causing axial advance of a cylindrical body with simultaneous axial rotation.

With the process of this invention there is the major advantage that in the production of large-diameter tubes the duration ofthc rolling cycle can be shortened substantially; this results in greater production capacity and a reduction of costs of installation. and therefore reduces the production expenses.

Moreover. time lost in changing mandrcls. is substantially eliminated so that the rate of production may remain substantially constant at all times.

In practice the materials used and the dimensions. may be as desired, according to requirements.

I claim:

1. Apparatus for rolling seamless tubes comprising:

a roll train having a plurality of roll stands defining a rolling axis;

a restraining device upstream of said roll train,

a mandrel attachable at the head end thereof to said restrain ng device.

a plurality of tubular tanks located between adjacent said roll stands on the rolling axis of said roll train and positioned so that a tube being rolled and said mandrel can pass therethrough during rolling.

inlet and discharge conduits connected to each said tubular tank, and

valves in said inflow and discharge conduits to control the inflow of coolant along said inlet conduits into said tubular tanks during cooling and to effect discharge of said coolant from said tubular tanks along said discharge conduits at the end of said cooling stage:

each said tubular tank having a discharge opening in the lowermost side thereof, and a vertically movable support positioned beneath each said discharge opening. means for running each said support between a raised position where said support closes said discharge opening and projects into said tank to provide support for said mandrel during cooling and a lowered position where said discharge opening is unobstructed whereby any water in said tanks is discharged therefrom.

2. The apparatus of claim I wherein there are provided further means for axially moving said mandrel separate from said restraining device. said further means operating to impart a rotation to said mandrel about its axis simultaneously with the longitudinal movement.

3. The apparatus of claim 1, wherein there are further provided means for moving said mandrel upstream from a position downstream of said roll train to insert said mandrel into an ingot or bloom located at said upstream end of said roll train.

4. The apparatus of claim 1, wherein each said tubular tank has an upper aperture through which coolant can overflow when said tanks are filled with coolant liquid. 

1. Apparatus for rolling seamless tubes comprising: a roll train having a plurality of roll stands defining a rolling axis; a restraining device upstream of said roll train, a mandrel attachable at the head end thereof to said restraining device, a plurality of tubular tanks located between adjacent said roll stands on the rolling axis of said roll train and positioned so that a tube being rolled and said mandrel can pass therethrough during rolling, inlet and discharge conduits connected to each said tubular tank, and valves in said inflow and discharge conduits to control the inflow of coolant along said inlet conduits into said tubular tanks during cooling and to effect discharge of said coolant from said tubular tanks along said discharge cOnduits at the end of said cooling stage; each said tubular tank having a discharge opening in the lowermost side thereof, and a vertically movable support positioned beneath each said discharge opening, means for running each said support between a raised position where said support closes said discharge opening and projects into said tank to provide support for said mandrel during cooling and a lowered position where said discharge opening is unobstructed whereby any water in said tanks is discharged therefrom.
 2. The apparatus of claim 1 wherein there are provided further means for axially moving said mandrel separate from said restraining device, said further means operating to impart a rotation to said mandrel about its axis simultaneously with the longitudinal movement.
 3. The apparatus of claim 1, wherein there are further provided means for moving said mandrel upstream from a position downstream of said roll train to insert said mandrel into an ingot or bloom located at said upstream end of said roll train.
 4. The apparatus of claim 1, wherein each said tubular tank has an upper aperture through which coolant can overflow when said tanks are filled with coolant liquid. 